Gas liquifaction

ABSTRACT

A gas under pressure enters a single counter-flow heat exchanger haVing a high pressure entrance side and a low pressure exhaust side, the gas from the high pressure side being connected in parallel to a number of Ranque tubes in which the gas expands. The hot and cold streams from the tubes are connected along the length of the low pressure side of the heat exchanger to progressively cool gas in the high pressure side until a small percentage of the gas can be flashed to liquid for storage.

United States Patent Foster-Pegg [4 1 June 27, 1972 [54] GASLIQUIFACTION 2,683,972 7/1954 Atkinson ..62/5

[72] Inventor: Richard W- Foster-Pegg, Warren, Pa. FOREIGN PATENTS ORAPPLICATIONS [731 Assigne= Enemy sysemsi 858,260 12/1952 Germany .Q..62/5 [22] Filed: Aug. 4, 1970 Primary Examiner-William J. Wye [2]]App! 60877 Attorney-William A. Drucker [30} Foreign Application PriorityData [57] ABSTRACT Aug. 6, 1969 Great Britain ..39,40l/69 A a nderressure enters a single counter-flow heat exchanger having a highpressure entrance side and a low [52] US. Cl ..62/5 pressure exhaustside, the gas from the high pressure side [51] f" Cl "Fzsb 9/02 beingconnected in parallel to a number of Ranque tubes in [58] Field ofSearch ..62/5 which the gas expands The hot and cold streams f the tubesare connected along the length of the low pressure side [56] Referencesand of the heat exchanger to progressively cool gas in the high UNITEDSTATES PATENTS pressure side until a small percentage of the gas can beflashed to liquid for storage. 1,952,281 3/1934 Ranque ..62/5 2,522,7879/1950 Hughes ..62/5 3 Claims, 2 Drawing figures P'A'TENTEDJUW 19123,572,179

sum 2 BF 2 GAS LIQUIFACTION BACKGROUND OF THE INVENTION Natural gas isfrequently expanded from pipeline pressure to a lower pressure fordistribution. At the same time, it is often desired to store liquifiednatural gas for use at periods of high demand. This is sometimesaccomplished by absorbing work from the gas as it expands to a lowerpressure and thus extracting heat to cool the gas. This systemconventionally requires rotating turbo machinery which requires skilledoperation, is costly, and is difficult to maintain.

SUMMARY OF THE INVENTION Accordingly to this invention, the rotatingequipment is replaced by a single heat exchanger and a number of staticRanque tubes. A gas at a given temperature expending through these tubesexhausts in two streams, one at a higher temperature and one at a lowertemperature. Depending on the initial temperature and pressure of thenatural gas or other gas being treated, it is indicated that, accordingto this invention, 1 percent or more of a gas may be liquified. If thegas is at a sufficiently high pressure, it may be expanded in seriesthrough a number of Ranque tubes with each tube being connected to thecold stream of the tube before it. Since the pressures required forseries expansion of natural gas are prohibitive, a heat exhanger isemployed with an inlet high pressure side and an outlet low pressureside. Progressively cooler gases from both the high and low temperaturestreams of each Ranque tube exhaust at suitable locations along the lowpressure outlet side of the heat exchanger to progressively coolcounter-flowing gas in the inlet side of the heat exchanger.Progressively colder gases are tapped from the inlet side of the heatexchanger to the Ranque tubes. At the end of the heat exchanger, aquantity of the gas is sufficiently cooled to be flashed to a liquid.

It is possible to replace the single heat exchanger with a number ofheat exchangers. A single high pressure feed line would then beconnected in parallel to a number of Ranque tubes with a heat exchangerusing the cold stream from each tube to cool the inlet stream to thefollowing tube.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic diagram of apreferred embodiment of this invention; and

FIG. 2 is a schematic diagram of another embodiment of this inventionusing a plurality of heat exchangers.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, naturalgas or the like, which is to be cooled by expansion, flows from inletpipe 1 into heat exchanger 2 having a high inlet pressure side 3separated from a low pressure exhaust side 4 by a heat conducting wall5. Progressively cooled gas flowing to the right as shown in side 3 istapped off the pipes 6-10 to the Ranque tubes 1 1-15.

The hot stream from tube 1 1 passes through pipe 16 to the low pressureexhaust or outlet pipe 26. The hot streams from tubes 12-15 passrespectively, through the pipes 17-20 to the low pressure outlet side 4of heat exchanger 2. The cold streams from the tubes 11-15 pass,respectively, through the pipes 21-25 to the outlet side 4 of heatexchanger 2. Pipes 17-25 lead into the exhaust side 4 of the heatexchanger 2 at suitable locations to progressively cool gas in the inletside 3. The gases in exhaust side 4 flow to the left as shown counter tothe direction of flow of the gases in the inlet side 3. Sufficientlycooled gas is drawn from the end of the inlet side 3 of the heatexchanger 2 through pipe 27 to be partially flashed into liquid 29 intank 30. Low pressure cooled gases pass from tank 30 through pipe 31 tothe exhaust side of heat exchanger 2.

As one example of this invention natural gas at 150 psig and 70 F. or530 R. flows from inlet pipe 1 into side 3 to be cooled and withdrawnthrough pipes 6-10 at temperatures of 496 R., 414 R, 347 R., 293 F., and246 R., respectively. The hot streams from tubes 11-15 flow throughpipes 16-20 at temperatures of 610 R., 510 R., 427 R., 360 R., and 302R., respectively. The cold streams from tubes 11-15 flow through pipes21-25 at temperatures of 407 R., 340 R., 285 R., 240 R., and 202 R.,respectively. The pipes 17-25 leading gas into the heat exchanger 2 atappropriate locations along the length of side 4 cool gas flowing fromside 3 through pipe 27 to 204 R. so that this gas may be flashed intoliquid in tank 30. Thegas leaving through pipe 26 is at 16 psig. It isto be noted that pipe 7, which has gas flowing into it at 414 R. is tothe right of pipe 21 which introduces a cooling gas at 407 R. into heatexchanger 2 to cool the gasentering pipe 7. Thus the temperature in heatexchanger 2 having counter-flow therein, decreases to the right as shownand the pipes enter and leave it accordingly. About 1 percent of thenatural gas treated in this manner may be Iiquified at the giventemperatures and pressures.

FIG. 2 shows a modification of this invention in which a gas from pipe50 at a high pressure is piped in parallel through pipe 51 and the heatexchangers 52-55 to the Ranque tubes 56-60, respectively. Pipes 61-64lead the cold stream from the tubes 56-59 to the heat exchangers 52-55respectively. Hot streams from the tubes 56-60 flow through pipes 65-69to an outlet 70. Warrned gases from heat exchangers 52-55 flow throughpipes 71-74 to outlet 70. Gases from the cold stream of tube 60 flowthrough pipe 75 to be flashed to liquid 76 in tank 77. Gases from tank77 may be flashed to liquid 76. in tank 77. Gases from tank 77 may passthrough pipe 78 to the outlet 70. It is to be noted that relatively coldgases in pipes 66-69 and pipe 78 may bepassed to a portion of a heatexchanger to help cool inlet gases and improve the efficiency of thisembodiment of the invention.

While all pipes and heat exchangers are shown as being of uniform size,these would be scaled according to the required flow therethrough andthe degree of heat exchange surface required.

What is claimed is:

1. Apparatus for flashing a small percent of a gas into a liquid onexpansion of the gas from a higher to a lower pressure, the apparatuscomprising, in combination,

a. a number of Ranque tubes connected in parallel to the gas at higherpressure allowing the gas to expand therein,

b. a hot and a cold outlet pipe from each Ranque-Hilsch tube,

c. counterflow heat exchanger means having at least one high pressureinlet cooling side and at least one low pressure outlet heating side,said cold outlet pipes conducting progressively colder gas to the atleast one heating side of said heat exchanger means to greatly cool asmall portion of the gas in said at least one inlet side, and

d. means flashing sufi'iciently cooled gas from said at least one inletside into a liquid.

2. The combination according to claim 1 wherein said heat exchangermeans has a single high pressure cooling inlet side, a single lowpressure heating side, and a heat conducting wall separating said highand low pressure sides, said Ranque tubes having inlet pipes connectedalong progressively colder portions of said inlet side of said heatexchanger means, said hot and cold outlet pipes leading to said outletside opposite higher temperature portions of said inlet side tosufficiently cool a percentage of said gas in said inlet side to beflashed into liquid in said means flashing gas into a liquid.

3. The combination according to claim 1 wherein said heat exchangermeans comprises a plurality of heat exchangers having inlet coolingsides and outlet heating sides, said inlet sides being connected inparallel to gas at a high pressure, cooled gas from said inlet sidespassing to said Ranque-Hilsch tubes for expansion therein, each of saidcold outlet pipes leading to a progressively colder heat exchanger, afinal one of said heat exchangers having an outlet side connected to aRanque tube having a cold outlet pipe from which gas is flashed intoliquid in said means flashing gas into a liquid, and

with the addition of a common low pressure outlet, said outlet sides ofsaid heat exchangers and said hot outlet pipes from said Ranque tubesbeing connected to said common low pressure outlet.

1. Apparatus for flashing a small percent of a gas into a liquid onexpansion of the gas from a higher to a lower pressure, the apparatuscomprising, in combination, a. a number of Ranque tubes connected inparallel to the gas at higher pressure allowing the gas to expandtherein, b. a hot and a cold outlet pipe from each Ranque-Hilsch tube,c. counterflow heat exchanger means having at least one high pressureinlet cooling side and at least one low pressure outlet heating side,said cold outlet pipes conducting progressively colder gas to the atleast one heating side of said heat exchanger means to greatly cool asmall portion of the gas in said at least one inlet side, anD d. meansflashing sufficiently cooled gas from said at least one inlet side intoa liquid.
 2. The combination according to claim 1 wherein said heatexchanger means has a single high pressure cooling inlet side, a singlelow pressure heating side, and a heat conducting wall separating saidhigh and low pressure sides, said Ranque tubes having inlet pipesconnected along progressively colder portions of said inlet side of saidheat exchanger means, said hot and cold outlet pipes leading to saidoutlet side opposite higher temperature portions of said inlet side tosufficiently cool a percentage of said gas in said inlet side to beflashed into liquid in said means flashing gas into a liquid.
 3. Thecombination according to claim 1 wherein said heat exchanger meanscomprises a plurality of heat exchangers having inlet cooling sides andoutlet heating sides, said inlet sides being connected in parallel togas at a high pressure, cooled gas from said inlet sides passing to saidRanque-Hilsch tubes for expansion therein, each of said cold outletpipes leading to a progressively colder heat exchanger, a final one ofsaid heat exchangers having an outlet side connected to a Ranque tubehaving a cold outlet pipe from which gas is flashed into liquid in saidmeans flashing gas into a liquid, and with the addition of a common lowpressure outlet, said outlet sides of said heat exchangers and said hotoutlet pipes from said Ranque tubes being connected to said common lowpressure outlet.